I really hope this doesn't become a requirement (i.e., law). I agree that RF is best, to the height and weight limits, *almost* always. However, I came here and to other forums, some specifically focused just on carseat safety, with the problems I had keeping my then-18 month old daughter in her RF convertible seat. The problem was that she was a houdini. Not only could she get her arms out - no matter how snug you made the straps - once she had her arms loose, when RF she would push up and out of the seat almost instantly. I contacted the manufacturer (Britax) and they had no suggestions. I tried everything I could think of and everything that was suggested. I even contemplated essentially sewing her into the thing, but felt that it would be too difficult to remove her in an emergency.
She also screamed hysterically and fought terribly hard any time we put her into the seat. It was heartbreaking. We minimized car travel as much as possible but our area is not served by public transportation and nothing is within walking distance.
Since she had passed the age and weight recommendations, we decided, reluctantly, to try FF. She stopped screaming and being hysterical about being put in the seat immediately. She was unable to push up and out of the seat, so while she still sometimes got her arms free, we had time to pull over and stop and get her in again before she was actually out of the seat.
She was about 19 mos at the time. I really don't regret it. We wanted to FF longer but it really seemed more unsafe to RF because she was so unhappy and escaping from the seat.
She's 3 and she's small enough that we could turn her RF again, but I'm wary of what her reaction would be. I've considered trying it. I may try it.
All I'm saying is that recommendations in situations like this are often better than laws, because laws don't take any individual situations into account. There should be some flexibility.
ETA: My son is totally different in the seat. He turned 1 recently and I anticipate keeping him RF to the limit (35 lbs). We aren't having ANY of the same problems.